Vacuum switch



J- S. HAWKINS July ,3, 1962 VACUUM SWITCH Fi led March 27, 1959 2SheetsSheet 1 M H r g INVENTOR- JACK S. HAWK/NS wa H/S ATTORNEY J. S.HAWKINS July 3, 1962 VACUUM SWITCH 2 Sheets-Sheet 2 Filed March 27. 1959IN VEN TOR JA GK 5. HA WK/NS H/S ATTORNEY 3,042,774 VACUUM SWITCHv JackS. Hawkins, San Jose, Calif., assignor, by mesnc assignments, toJennings Radio Manuiacturing Corporation, San Jose, Calif., acorporation of Delaware Filed Mar. 27, 1959, Ser. No. 802,478 19 Claims.(Cl. 20 -104) My invention relates to multiple pole-double throwswitches or relays, and particularly to a three poledouble throwminiature vacuum switch or relay.

One of the objects of the invention is the provision of a switch themajor portion of which may be brazed in one operation, thus decreasingproduction time and ultimate cost.

' Another object is the provision of a vacuum switch in which finaladjustment is unnecessary.

Another object of the inventionis the provision of a double-throw vacuumswitch having a built in snap-action of the movable contact in bothdirections.

Still another object is the provision of a solenoid operated vacuumswitch requiring less coil power than conventiorral solenoid operatedswitches.

A still further object is the provision of a vacuum switch havinggreater contact pressure and greater contact area than comparableswitches.

Still another object is the provision of a miniature vacuum switchsuitable for low and medium voltage three-phase industrial and missileapplications.

Another important object is the provision of a miniature threepole-double throw vacuum switch in which the contacts of one section ofthe switch are effectively shielded from the contacts of the othersection, thus permitting three-phase make and break operation in thesame envelope.

The invention possesses other objects some of which with the foregoingwill be brought out in the following description of the invention. I donot limit myself to the showing made by the said description and thedrawings, since I may adopt variant forms of the invention within thescope of the appended claims.

Referring to the drawings: k

FIG. 1 is a vertical half section-a1 view taken in the plane indicatedby the line 1-1 in FIG. 2.

FIG. 2 is a plan view showing the arrangement of external terminals.

FIG. 3 is a vertical half sectional view of a dielectric ring and themovable contact ring in assembled position prior to being brazed. The bythe line 3-3 in FIG. 7.

FIG. 4 is a view similar to FIG. 3, but showing the dielectric andmovable contact ring assembly after brazing and cooling and showing thecontact ring snapped into its upper position.

FIG. 5 is a vertical half sectional view of the dielectric and movablecontact ring assembly showing the contact ring snapped into its lowerposition.

FIG. 6 is a vertical half sectional view of one of the fixed terminalrings shown brazed to a dielectric ring.

FIG. 7 is a plan view of the contact ring detached from the assembly andillustrating the relationship between the inner periphery and contactarea thereof.

FIG. 8 is a fragmentary sectional view of one of the dielectric rings,with a terminal ring attached, and illustrating the shield meansinterposed between the inner periphery of the dielectric ring and theswitch contacts.

FIG. 9 is a fragmentary vertical sectional view illustrating the closeconfinement of. the dielectric bushings by the inner peripheries of theterminal and contact rings. f

FIGS. 1 through 7 are drawn to a scale approximately three times. actualsize, FIG. 8 is drawn'to a scale ap proximately tweleve times actualsize, and FIG. 9 is enlarged approximately six times actual size.

atent plane of section is indicated The exacting requirements whichconventional switch gear must meet in order to insure its reliabilityand suitability for incorporation in modern environments such as land,sea, air and space equipment, results in the virtual necessity of handprocessing each conventional device to bring it within the closetolerances necessary for reliable operation. This custom processingincreases production time and cost, and necessitates elaborate testingand inspection procedures to insure compliance with requirements. It istherefore the broad object of the present invention to provide a switchin which the elements are of a nature permitting sub-assembly thereofand heating to brazing temperatures to integrally and hermetically unitethe sub-assemblies into composite units requiring very little additionalassembly or further processing. The brazing temperatures utilized are ofa magnitude to adequately heat treat those elements requiring such treatment.

Broadly considered, the vacuum switch of my invention comprises anevacuated envelope formed by a series of axially aligned dielectricrings, preferably metallized ceramic, having metallic terminal andcontact rings integrally and hermetically interposed therebetween in aselected cooperative relationship. Each opposite end of theceramic-metal ring complex is hermetically closed by a metallic endplate structure integrally brazed to an end ceramic ring of theceramic-metal ring complex. Within the envelope thus formed are providedfixed and movable contacts integral, respectively, with the terminal andcontact rings, and movable into and out of engagement to make and breaka circuit through selected pairs of such rings. Armature means areprovided within the envelope cooperating with an energizable coiloutside the housing for effecting movement of the movable contact. Toprevent the deposit of conductive vaporized contact metal on the innerperiphery of each ceramic ring, which if permitted to. accumulate willbuild up a conductive path between adjacent terminal and contact rings,each ceramic rings is provided with an integral shield which cooperateswith associated surfaces to prevent the accumulation of a continuousconductive layer. A tubulation for evacuating the envelope is providedon one ofthe end plate structures, and a block of dielectric materialembedding the tubulation and the associated end plate structure,provides protection for the tubulation and also serves to supportexternal terminals conductively connected to the terminal and contactrings, and providing convenient means for connecting the switch into acircuit.

In more specific terms, the miniature high power vacuum switch of myinvention comprises a plurality of annular ceramic rings 2 havingopposite metallized sides 3. On its inner peripheral surface 4, eachceramic ring is provided with an integral concentric reentrant flange 6,radially spaced inwardly approximately 0.015" from the surface 4 of theceramic ring and constituting a shield against vaporized contactmaterial. In a ceramic ring such as the one illustrated, in which theheight ranges from 0.086" to 0.088 and the radial thickness amounts toapproximately-'0.21 7", the differentiation in height between ceramicring and shield flange may conveniently range from 0.010" to 0.017".

Hermetically brazed about its outer peripheral portion between adjacentceramic rings of selected pairs thereof and axially aligned therewith,is an annular metallic terminal ring 7. The ring is provided with anintegral nular portion 9 provided adjacent its inner periphery 12 withan integral concentric contact 13. The terminal ring is preferablyfabricated from thin gauge NiFe alloy having a rate-of contractionsomewhatgreater than the rate aoeavva of contraction of the ceramicrings to which it is brazed.

During heating the two materials expand at respective rates. Afterheating and brazing to integrally unite the parts, the joined parts aresimultaneously cooled. Since the parts are now integrally united, theycan no longer contract at their respective rates. The rate ofcontraction of each is now modified by an interdependence upon preventedfrom contacting as much as: it had expanded,

and the resulting tension in the NiFe ring draws the ring tightly acrossthe ceramic ring, thus causing the ceramic ring to be compressed. Thisphenomenon is illustrated quantitatively in FIG. 6, where the distance Brepresents the amount, greatly exaggerated, which the terminal ring isprevented from contracting, and the distance C represents the amount,again greatly exaggerated, which the ceramic ring is compressed bytension in the NiFe ring.

The ceramic-metal ring complex is completed by hermetically andintegrally interposing between the pairs of ceramic rings carrying theterminal rings, an annular metallic contact ring 14. This ring isaxially aligned with the ceramic rings and terminal rings and isprovided with a radially outwardly extending apertured lug 16constituting an external terminal lead. Within the ring assembly thecontact ring is provided with an integral inwardly extending annulardomed portion 17 provided adjacent its inner periphery 18, and on bothsides of the ring, with integral concentric contacts 19 axially alignedwith and adapted to engage with and disengage the fixed contacts 13 onthe juxtaposed terminal rings. The contact ring 14 is distinguished fromthe terminal rings 7 by having a slightly smaller central aperture, asbest shown in FIG. 1, and by being fabricated from a dilferent material.

The contact ring 14 is fabricated from thin gauge molybdenum in sheetform, which when stamped into the form shown in FIG. 3 and assembled asan element in the ceramic-metallic ring complex exhibits characteristicsmarkedly difierent from those exhibited by the terminal rings. Incomparison with the ceramic rings to which it is brazed, the molybdenumcontact ring expands andcontracts less than the ceramic rings withvariations in temperature. After heating and brazing, the integrallyjoined parts are cooled simultaneously, whereupon the relatively greaterand more rapid contraction by the ceramic rings causes a radiallyinwardly directed compressive force to be exerted on the outerperipheral portion of the molybdenum contact ring, thus causing theradially inwardly extending annular portion 17 to compensate for arelatively less and slower contraction by being displaced into a domedshaped. FIGS. 3 and 4 illustrate the relationship of the parts beforeand after heating to a brazing temperature and subsequent cooling. Aswith the terminal rings, this phenomenon is illustrated quantitativelyin FIG. 4, where the distance A represents the amount, again greatlyexaggerated, which the ceramic rings force the molybdenum contact ringto contract. The distance D represents, greatly exaggerated, the amountthe ceramic rings are prevented from contracting by the compressivestress created in the molybdenum contact ring.

To form the ceramic-metal ring complex, the terminal and contact rings,both flat, are stacked with the individual metallized ceramic rings withbrazing compound applied, in the relationship shown in FIG. 1. Thisassembly is then heated in an oven to a high brazing temperature atwhich temperature the contiguous portions of ceramic and metal ringshermetically coalesce into a light weight unitary complex of greatrigidity. Upon being cooled and removed from the oven, it will be foundthat the different contraction coeflicients of the ceramic, terminal andcontact rings have eitected tensioning of the terminal ring andcompression of the contact ring as previously described.

As illustrated in FIGS. 1, 4 and 5, compressing the side of the plane ofthe outer periphery of the ring. If

pressure is now applied to the convex side of the displaced centralportion of the contact ring in a direction parallel to the axis thereof,the contact-carrying annular portion will be caused to snap to theopposite side of the plane of the outer periphery of the contact ring.It has been found that to efiect such side-to-side displacement,pressure need be applied only until the annular portion is just past theplane of the outer periphery. The compressive stress built up in theannular portion by bringing it into this position then exerts itself tosnap the annular portion to its outer extremity. These alternatepositions are illustrated in FIGS. 4 and 5. As will be apparent fromFIG. 1, when the contact ring is displaced to either side, one of itscontacts 19 abuts the fixed contact 13 arranged on a juxtaposed terminalring. The parts are proportioned so that resilient abutting en-'gagement is effected before the contact ring reaches its outerextremity. This results in the contacts 19 on the contact ring beingresiliently pressed hard against the fixed contacts by the inherentresilience of the compressed contact ring. Faster closing, lessvibration and reduced contact resistance thus result.

Hermetically closing one end of the hollow ceramicmetal ring complex isan end plate structure comprising an annular plate 21 brazed to the enddielectric ring, and provided with an outwardly extending integralcylindriwl flange 22. Supported on the annular plate 21 and fittingsnugly within the cylindrical flange is a cover plate 23 having a raisedcentral portion 24 and a cylindrical peripheral flange 26 concentricwith the flange 22. The outer ends of both flanges are flush and lendthemselves to heliarc brazing to hermetically seal this end of thehollow ceramiemetal ring complex. Brazed to the cover plate andcommunicating with the interior of the hollow complex is a tubulation 27useful for evacuating the switch envelope.

Hermetically sealing the other end of the hollow ceramic-metallic ringcomplex is another end plate structure comprising an annular plate 28hermetically brazed to the end dielectric ring and provided with anintegral cylindrical flange 29 extending from its outer periphery. Aradially outwardly extending integral flange 31 cooperates with thecylindrical flange 29 to form a seat on which is integrally andhermetically supported the inner end portion of a hollow cylindricalhousing 32. A radially outwardly extending flange '33 brazed on thehousing adjacent its inner end is provided to lie against the flange 31.The-outer peripheries of the flanges 31 and 33 are flush and facilitateheliarc brazing to hermetically seal this union. I-Ieliarc brazing atthis point and also at the peripheries of flanges 22-26 permit easydisassembly of the switch for salvage pm'poses or repairs, whileinsuring an integral composite construction of light weight and greatrigidity. The housing is preferably fabricated from magnetizable steel,and is provided on its inner end portion with a radially inwardlyextending integral flange 34, and at its other end with a detachablemagnetizable cover plate 36.

Hermetically sealing the inner end of the hollow cylindrical housing isa non-magnetizable transverse wall 37.

i The wall is annular in form and spaced intermediate the ends of thehousing, the outer peripheral portion of the wall being integrally andhermetically brazed to the housing wall, while the inner peripheralportion of the wall is integrally and hermetically united to amagnetizable core 38. The outer end of the core cooperates with thedetachable cover plate 36 to detachably retain and enclose anenergizable coil 39 within the hollow housing 32. Terminals 41,extending through the cover plate provide means for connecting the coilwith control circuit leads 42. A screw 43 threaded into the outer end ofthe core clamps the cover plate to the core and housing to complete themagnetic path at this end of the housing. I

Within the evacuated hollow chamber means are provided responsive to themagnetic field generated by the energized coil to move said movablecontact into and out of engagement with adjacent fixed contacts.Armature 44 positioned for axial movement within the envelope betweenthe annular plate 23 and the inner ends of housing 32 and core 38,carries a centrally disposed perpendicular stem 46 brazed at its lowerend on the armature and threaded at its upper free end to receive aclamp nut 47.

Detachably mounted on the stern are a pair of upper and lower axiallyaligned interengaging dielectric bushings or sleeves 48 and 49. As shownin FIG. 1, interengagement of the bushings is effected by a reducedsection 51 of bushing 48 seated in a rabbet in bushing 49. A shoulder 52formed in the bushing 48 cooperates with an adjacent portion of thereduced section and the upper end of the bushing 49 to provide acircumferential groove 53 into which the inner peripheral portion 13 ofthe movable contact ring extends to a loose sliding fit with thatportion of the reduced section 51 constituting the bottom of the groove.The clamp nut 47 retains the bushings in the relationshipshown,'however, if desired the bushings may be integrally united as bybrazing. Acoil' spring 54 interposed between the armature and the wall37 resiliently urges the armature away from the inner end of the coreand into the position shown.

To mount the switch, a stop collar 56 and a threaded sleeve 57 arebrazed to the housing adjacent the flange 33. The sleeve and stop collarcooperate'with a lock Washer 58 and nut 59 to detachably mount theswitch in an apertured panel 61, shown in dash lines.

Means are provided protecting the end plate structure ill-26 and thetubula-tion attached thereto from accidental injury, and also providinga means for supporting and connecting the external terminal tabs 8 and16 into a circuit. Molded about the upper end plate structure 2l26, is ablocl; 62 of synthetic resinous material of high dielectric strength.The block conforms to the shape of the end plate structure, and isprovided with conductive terminal plugs 63; embedded therein atcircumferentially equally spaced intervals as shown FIGS. 1 and 2. Thelower end 64 of each terminal plug extends below the bottom of the block62. an amount corresponding to the distance the associated terminal tabis spaced therebelow, and a screw 66 detachably and conductively secureseach external tab to. the associated terminal plug. The upper end ofeach terminal plug is bored and tapped as at 6 7 to provide a connectingmeans for leads of the circuit to be controlled.

In operation, the switch contacts are resiliently retained in theposition shown by the pressure exerted by the domed contact ring tendingto expand to its outermost limit. Energizing the coil causes a magneticfield to be 4 generated, which pulls the armature and attached stemdownwardly into engagement against the inner end of the core and housingand thus completes the magnetic circuit. Downward movement of the sterncauses the inner peripheral portion of the contact ring to be engaged bythe shoulder 52, which flexes the domed contact ring inwardly until itjust passes the plane of the outer peripheral portion. At this point thecontact ring tends to snap downwardly to the extreme position shown inFl G. 5. Before it reaches this position, however, it engages the fixedcontact 13, and with its own intrinsic resilience added to that of themagnetic force pulling on the arma- It should be noted that uponseparation of the movable contact from the fixed contacts, any vaporizedcontact material resulting from the formation of an arc is preventedfrom migrating past the inner peripheries of the terminal rings or thecontact ring by theclose confine ment of the dielectric bushings by theinner peripheries of these rings. The terminal and contact ringscooperating with the bushings and ceramic rings 2, thus provide twosubstantially isolated contact chambers within which vaporized contactmetal is contained. As shown best in FIG. 8, the shield 6 on eachceramic ring 2 prevents deposit of a continuous conductive layer of suchvaporized metal. It has been found that vaporized contact metal willadhere to the inner periphery of the shield and to a portion of theinner periphery of the ring itself, but such vaporized material will notmigrate into the channel between the shield 6 and ring 2. Vaporizedcontact metal is thus caused to condense in a manner which precludesformation of a conductive path between the terminal and contact rings.

I claim: 1

1. A vacuumized switch comprising a plurality of metallized dielectricrings, a metallic terminal ring interposed between two adjacentdielectric rings, a contact ring spaced from said terminal ring andsupported on one of said dielectric rings and movable into or out ofengagement with said terminal ring, said terminal and contact ringsbeing integrally united to the associated dielectric rings to form ahermetically tight ring assembly, an end plate structure hermeticallyclosing each opposite end of the ring assembly to form a hermeticallysealed envelope, and switch actuating means supported on said envelopeand operatively connected with the contact ring to selectively move thecontact ring into or out of engagement with said terminal ring to makeor break a circuit therethrough.

2. The combination according to claim 1, in which said terminal ring isprovided with radially inwardly and outwardly extending portionsproviding respectively a fixed contact within the envelope and aterminal lead outside the envelope.

3. The combination according to claim 1, in which one of said end platestructures includes an annular plate, a hollow housing integrally unitedthereto adjacent its inner periphery, a transverse wall integrallyinterposed hermetically between the ends of the housing, and amagnetizable core fixed on said wall and extending on both sidesthereof.

4. The combination according to claim 1, in which said contact ring isprovided with radially inwardly and outwardly extending portionsproviding respectively a movable domed contact portion within theenvelope and a terminal lead outside the envelope.

5. The combination according to claim 1, in which said switch actuatingmeans includes an energizable coil outside the envelope, a coreextending into the envelope and said coil, a coil-responsive armaturemovably supported within the envelope, and spring means normally ilrgingthe armature away from the core within the enveope.

6. The combination according to claim 4, in which shield means areprovided integral with said dielectric rings and interposed between saiddielectric rings and said domed contact portion of the contact ring.

7. The combination according to claim 4, in which -means are providedelectrically insulating said switch actuating means from said terminaland contact rings.

8. The combination according to claim 4, in which said switch actuatingmeans includes" an energizable coil outside the envelope and acoil-responsive armature movably supported within the envelope, saidarmature having a stem fixed thereto and to said movable domed portionof the contact ring to effect movement thereof in one direction whensaid armature moves in response to said energized coil, and spring meanswithin the envelope to move the armature and said domed contact portionof the contact ring in the opposite direction when said coilisdeenergized.

9. The combination according to claim 4, in which a terminal ring isprovided spaced on each side of said contact ring and movement of saiddomed contact portion of the contact ring in one direction makes a firstcircuit through one terminal ring and movement of said domed contactportion in the opposite direction breaks said first circuit and makes asecond circuit through the other terminal ring.

10. The combination according to claim 9, in which said contact ring iselectrically insulated from said terminal rings by said dielectric ringsand therewith and with said terminal rings form first and secondchambers within which said first and second circuits, respectively, aremade and broken.

11. In a vacuumized switch, the combination comprising a plurality ofaxially arranged dielectric rings, a terminal ring integrally united tocorresponding sides of alternate dielectric rings and having radiallyinwardly and outwardly extending portions constituting fixed contactswithin the envelope and terminal leads outside the envelope, a contactring integrally united to the corresponding side of an intermediatedielectric ring and having radially inwardly and outwardly extending portions constituting a movable contact within the envelope and a terminallead outside the envelope, said movable contact portion movable in onedirection to engage one of said fixed contacts and movable in theopposite direction to engage another fixed contact.

12. In a vacuumized switch, the combination comprising a metallizeddielectric ring, and an annular contact plate constituting an' electricconductor extending thereacross having inner and outer peripheralportions, said outer portion being integrally united to said metallizeddielectric ring, the remainder of said plate being progressively ofisetbetween said outer and inner peripheral portions and to one side of theplane of said outer peripheral portion to form a domed inner peripheralportion lying on one side of a plane coincident with said outerperipheral portion and movable from one side of said plane to the other.

13. In a vacuumized switch having fixed and movable contacts, a flatdielectric ring comprising a main body portion of rectangular radialsection and having a reentrant flange integral with the inner peripheryof said body portion and interposed between said contacts and said innerperiphery.

14. The combination according to claim 13, in which the height of saidflange is less than the height of said body portion.

15. The method of displacing a portion of a flat plate to produce a dometherein comprising the steps of arranging a flat plate having apredetermined coefiicient of linear expansion on an annular base havinga predetermined relatively higher coeflicient of linear expansion,

heating the plate and base to a brazing temperature, brazing the plateto the annular base at such temperature, and subsequently cooling theplate and base so brazed whereby the difference in linear contraction ofthe base exerts a radially inwardly directed compressive force on theplate to effect doming of said plate.

16. The method of integrally uniting and conditioning two spaced andinitially parallel plates to effect tensioning of one and compression ofthe other to form a dome therein comprising the steps of arranging oneplate having, a predetermined coeflicient of linear expansion on oneside of an annular base having a predetermined relatively lowercoefiicient of linear expansion, arranging the other plate having apredetermined coefficient of linear expansion relatively lower than saidannular base on the other side of said base from said first mentionedplate, heating the assembly of plates and base so arranged to a brazingtemperature, brazing the plates to the base at such temperature, andsubsequently cooling the brazed assembly of plates and base to effectcontraction of said plates and base by varying amounts whereby one ofsaid plates is tensioned and the other plate is compressed to form adome therein.

17. The method recited in claim 16, in which said plates are annularmetallic membranes and said base com prises a ceramic ring.

18. The method recited in claim 16, wherein said base comprises aceramic ring metallized on two opposite sides, and a brazing medium iswiped on the sides of said ceramic ring prior to assembly of said platesthereon whereby said plates are hermetically and integrally fused tosaid ceramic ring by said brazing medium when said brazing temperatureis attained.

19. In a vacuumized switch, the combination comprising a metallizeddielectric ring, a flat annular conductive contact plate extendingthereacross and having an outer peripheral portion integrally united toone side of said ring, a second annular conductive contact plateextending across the opposite side of said dielectric ring and having anouter peripheral portion integrally united thereto and having a domedinner peripheral portion lying on one side of a plane coincident withsaid opposite side of said ring and movable from one side of said planeto the other to selectively make or break electrical contact between rsaid flat and domed conductive plates.

References Cited in the file of this patent UNITED STATES PATENTS1,117,347 Dixon Nov. 17, 1914 1,571,630 Japolsky Feb. 2, 1926 1,931,475Brasch et a1 Oct. 17, 1933 2,391,238 Herman Dec. 18, 1945 2,886,668Steward et a1. May 12, 1959 FOREIGN PATENTS 723,123 France Apr. 4, 1932787,846 Great Britain Dec. 18, 1957

